Hard ductile alloy



Filed April 9', 1954 INVENTOR. I

ATTORNEYS.

United States PateiitO 2,821,474 HARD'DUCTILE AhllbY Marvin L.Steinbuch, Cincinnati, Ohio, assignor to The Lunkenheimer Company,Cincinnati, Ohio, a corporation of Ohio Application April 9, 1954,Serial No. 422,081 4 Claims. (Cl. 75--171) type of alloy is disclosed inUnited States Patent No.

2,245,566, issued June 17, 1941, for Welding Rod; it comprisessubstantially 6 to 12% silicon, 9 to 30% chromium and the balancenickel.

Castings made from such an alloy are too hard to be machined by turningor boring in the usual manner, and therefore, they must be formed toshape by grinding. Because of its extreme hardness and wear resistance,such an alloy is potentially useful where such characteristics aredesirable, as in the seats of valves which are required to withstand theabrasion incidental to the flow of fluids sometimes under high velocityand pressure. However, if valve seats in the form of castings are madefrom such an alloy and are brazed in position in the valve structure.the heat of brazing causes, or may cause, slight warpage, cupping ordistortion of the seat elements to occur, there by defeating theprecision with which the seat element initially may have beenfabricated. The alloy of the identified patent is not suflicientlyflexible, or it is too lacking in ductility, to be distortedsufliciently to overcome the warpage, and the pressure exerted on adistorted alloy metal seat by the valve closing means is apt to cause itto fracture or break. Thus, although the total amount of distortioncaused by the heating incidental to the brazing of the piece mayactually be very small, still the brittleness of the alloy is high andit cannot reliably survive the small deflection which is requisite tophysically distort the cast element to its original state.

I have discovered that nickel-chromium-silicon alloys having a hardnessand wear resistance desirable for valve seats can be made sufficientlyductile to permit any warpage incidental to the brazing operation to beovercome by physical force, incorporating therein a minor percentage ofcopper which does not exceed substantially by weight of the alloy.Although the silicon content of the alloy shown in the aforesaid patentis relatively high, the addition of the copper does not cause silicionprecipitation as would normally be expected. Most significantly, theincorporation of copper in the alloy does not impair hardness, but doesincrease ductility, the increase in ductility being roughly proportionalto the amount of copper utilized.

A typical example of the use of the alloy in a valve structure isdisclosed in the accompanying drawing, although it is to be understoodthat the alloy may be used for any purpose where hardness and ductilityare both desired.

The figure of the drawing is a sectional view of an otherwiseconventional globe valve structure. In the drawing, 10 indicates thebody casting. Within the casting is the seat diaphragm 11 separating thetwo ends of the valve, in which is located aperture 13. An aperturedvalve seat element 14 is mounted in a seat recess in the diaphragmportion .15 and is secured in position bya braze 16, conventionallysilver. Mounted over the valve seat 14;?is bonnet 17 and stem 18 .on theouter end of which is the valve ,handle 19. .Swiveled to'the lower endof the stem is the movable valve element 20 on which a valve seatelement 21 is mounted and secured by a "braze 22. Valve seats 14 and 21are fabricated from the alloy herein described.

The valve seat elements are fabricated from the alloy by castingthereof, after which they are ground to shape and then brazed inposition, as by silver soldering. The seat elements may be of anydesired shape; for example, they may be in the form of thin annularrings having ground or ground and lapped facial surfaces, which areengageable with one another.

If these discs become distorted or cupped as a result of the heat towhich they are subjected when being brazed in place in the valve body,then, when the valve handle is operated to close the valve, the seatswill not initially engage one another over their entire facial areas asintended. However, by exerting somewhat greater closing force on thevalve handle either one or both of the disc elements will flexsufliciently, without breaking, to permit them to be brought intocomplete facial engagement. In this manner the valve may be closedcompletely due to the inherent ductility of thenickel-chromium-siliconcopper alloy.

In general, the alloy should comprise from one-half percent to 5%copper, 6 to 12% silicon, 9 to 30% chromium and the balance nickel. Forvalve seat castings the preferred alloy comprises 4 /2 to 5% copper byweight, 7 to 10% silicon, 15 to 20% chromium and the balance nickel.

A comparison of typical alloys disclosed in United States Patent No.2,245,566 and the alloys of the present invention indicates the degreeto which ductility may be attained without sacrifice of hardness.

Deflection, as given in this table, is the deflection of a A inchdiameter cast round rod of alloy held firmly at one end, the deflectionbeing measured at a point 6 inches from the point at which the rod isheld.

Like the composition shown in the aforesaid United States Patent No.2,245,566, the alloys of the present invention are adapted for use inwelding, but unlike the previous compositions, the alloys of the presentinvention provide improved ductility in weld deposits as well as extremehardness and resistance to abrasion. The invention, therefore,contemplates alloys which are made in the form of welding rods, andweldments fabricated therefrom, as well as castings for valve seats andother uses where ductility is required in combination with hardness andabrasion resistance.

Having described my invention, I desire to be limited only by thefollowing claims:

1. A valve seat comprising a casting of an alloy consisting essentiallyof /2 to 5% copper, 6 to 12% silicon, 9 to 30% chromium, and the balancenickel.

2. A valve seat comprising a casting of an alloy consisting essentiallyof 4 /2 to 5% copper, 7 to 10% silicon, 15 to 20% chromium, and thebalance nickel.

3. A valve seat thermally bonded to a seat support, said valve seatbeing formed of a hard ductile alloy consisting essentially of xi to 5%copper, 6 to 12% silicon, 9 to 30% chromium, and the balance nickel.

4. A valve seat thermally bonded to a seat support, said valve seatbeing formed of a hard ductile alloy consisting essentially of 4 /2 to5% copper, 7 to 10% silicon, 5 15 to 20% chromium, and the balancenickel.

1,115,239 Parr Feb. 27, 1914 10 Brix Oct. 31, 1916 Spitzley et a1 June8, 1926 Spitzley et al June 8, 1926 Spitzley et al June 8, 1926 EgebergFeb. 15, 1938 Bolton June 17, 1941 Norton Sept. 3, 1946 Wissler Sept. 5,1950

1. A VALVE SEAT COMPRISING A CASTING OF AN ALLOY CONSISTING ESSENTIALLYOF 1/2 TO 5% COPER, 6 TO 12% SILICON, 9 TO 30% CHROMIUM, AND THE BALANCENICKEL.